Virtualization technology provides a mechanism for optimizing processing at a computer. Virtualization technology provides a software layer that when executed allows multiple virtual machines with, in some cases, different operating systems to run side-by-side with other virtual machines running on the same physical machine (e.g., a node, a computer, a processor, a server, a blade, and the like). The virtualization software provides a so-called “container” that wraps and isolates the virtual machine from other virtual machines. For example, in a server complex including fifty physical servers, each of which hosts its own application server, virtualization permits the server complex to instead operate with, for example, twenty-five physical servers, each of which includes virtualization software providing two virtual machines for the application servers. In both cases, fifty application servers are deployed, but with virtualization, the number of physical servers is reduced to twenty-five. Virtualization software may provide one or more of the following functions: running multiple virtual machines with different operating systems at the same time on the same physical machine; generating fully configured isolated virtual machines with a set of virtual hardware including an operating system and applications; saving, copying, and provisioning of virtual machines; and moving virtual machines from one physical machine to another physical machine for workload management.
When a virtual machine is used, the virtual machine may include an operating system. The operating system may include one or more programs, such as applications. An operating system (OS) is the program that, after being initially loaded into the computer by a boot program, manages other programs on the computer. The other programs (also referred to herein as application programs or applications) may use the operating system by making requests for services through one or more application program interfaces (APIs) of the operating system. A program (or application) may perform one or more specific functions (or tasks) directly for a user or, in some cases, another program. A virtual machine may include an operating system, such as Linux or Windows Vista, and one or more applications, such as a browser, all of which operate in the so-called “container” provided by the virtual machine.
In some cases, the virtual machine may also include some data for use by at least one of the operating system and the application. When this is the case, the virtual machine may be referred to as a “virtual appliance.” The phrase “virtual appliance” refers to an example of a virtual machine that may include the application, operating system, and data (e.g., application data, configuration information, drivers, and the like) to enable simplification of the installation and the configuration process associated with running the application. An example of a virtual appliance is the MediaWiki software that powers Wikipedia, which is available as a virtual appliance. The MediaWiki appliance contains all the necessary software, including operating system, database, and MediaWiki, to run a wiki installation as a so-called “black box.”